there is no such thing as a dumb post if you suffer from anxiety anything and everything can make you stressed and i understand you just need someone to reassure you that everything is alright.
and everything is alright.
saline sprays cannot harm you in anyway, that is if they are your own, i don't see you trading them between people
so there is no way to contract a cold from them.
you cannot get sick again from using the saline spray as your body becomes immune to the virus or what ever ills you and then the virus becomes defective and dies within hours.
which means that the saline spray is totally clean after you use it, so don't be afraid of getting sick once again after you become healthy.
also saline spray can do no damage to your body it might make your nose to moist if you down bottles of it
saline spray does not go right to your brain, all the water is purified so don't worry about it.
so all in all everything is perfectly fine.